The present invention relates to a ball screw apparatus used in a machine tool, a semiconductor fabricating apparatus, a board mounting machine and the like.
In a machine tool, a semiconductor fabricating apparatus, a board mounting machine or the like, there is used a ball screw apparatus of a tube circulating type as shown by JP-A-2003-269564, shown below, in a related art as an apparatus of converting rotational movement into linear movement. However, the ball screw apparatus adopts a system of scooping up to circulate a ball rolling between ball screw grooves formed at an outer peripheral face of a screw shaft and an inner peripheral face of a nut by a tongue portion of a circulating tube and therefore, there poses a problem that vibration or noise is brought about when the ball collides with the tongue portion of the circulating tube.
In order to resolve the problem, in Japanese Utility Model No. 3034052, shown below, there is disclosed a ball screw apparatus of scooping up a ball rolling between ball screw grooves of a screw shaft and a nut in a tangential direction of a ball center track circle by a ball scoop up portion of a ball circulating member integrated to an end portion of the nut and introducing the scooped up ball to a ball return path formed at the nut to circulate.
However, according to the ball screw apparatus described in Japanese Utility Model No. 3034052, mentioned above, a ball guide path for guiding the ball scooped up in the tangential direction of the ball center track circle to the ball return path of the nut is formed only by the ball circulating member. Therefore, when a groove interval between the ball screw grooves is narrow or when the ball screw grooves are constituted by multistreak screw grooves, a containing recess portion of the ball circulating member formed at an end portion of the inner peripheral face of the nut interferes with the ball screw groove on a side of the nut and therefore, there poses a problem that a diameter of the ball needs to be reduced in order to prevent interference between the containing recess portion and the ball screw groove on the side of the nut. Further, according to the above-described ball screw apparatus, there is needed a circular arc shape spring ring for fixing the ball circulating member to an axial direction of the nut and therefore, there poses a problem that a number of parts is increased.